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Abstract:

Disclosed are composite structures having improved heat aging, processes
for making them, and end use articles. The composite structures comprise
a polyamide matrix resin composition comprising copper based heat
stabilizer; a fibrous material and a polyamide surface resin composition
comprising surface heat stabilizer; wherein the surface heat stabilizer
is different than the copper based heat stabilizer.

Claims:

1. A composite structure comprising: a polyamide matrix resin composition
comprising from 0.1 to at or about 3 weight percent of a copper based
heat stabilizer based on the weight of the polyamide matrix resin
composition; a fibrous material selected from woven or non-woven
structures, felts, knits, braids, textiles, fibrous battings or mats, and
combinations of these; and a polyamide surface resin composition
comprising 0.1 to 3 weight percent of a surface heat stabilizer based on
the weight of the polyamide surface resin composition; wherein: the
surface heat stabilizer is different than the copper based heat
stabilizer; and wherein the fibrous material is impregnated with the
polyamide matrix resin composition.

2. The composite structure of claim 1 wherein the polyamide in the matrix
resin composition and the polyamide in the surface resin composition, are
independently selected from the group consisting of PA6; PA11; PA12;
PA4,6; PA6,6; PA,10; PA6,12; PA10,10; PA6T; PA6I, PA6I/6T; PA6,T/6,6;
PAMXD6; PA6T/DT and copolymers and blends of the same.

3. The composite structure of claim 1 wherein the surface heat stabilizer
is selected from the group consisting of dipentaerythritol,
tripentaerythritol, pentaerythritol and mixtures thereof.

4. The composite structure of claim 1 wherein the copper based heat
stabilizer is a mixture of 10 to 50 weight percent copper halide, 50 to
90 weight percent potassium iodide, and from zero to 15 weight percent
metal stearate.

5. The composite structure of claim 1 wherein the fibrous material is
from 30 weight percent to 60 volume percent of the composite structure.

6. The composite structure according to claim 1 wherein the surface resin
composition and/or the matrix resin composition further comprise one or
more impact modifiers, one or more oxidative stabilizers, one or more
reinforcing agents, one or more ultraviolet light stabilizers, one or
more flame retardant agents or mixtures thereof.

9. The article of claim 7 in the form of automotive powertrain covers and
housings, engine cover brackets, steering columns frame, oil pans, and
exhaust system components.

10. A process for making a composite structure of claim 1, the process
comprising the step of: impregnating the fibrous material under heat and
pressure with the polyamide matrix resin wherein at least a portion of
the surface of the composite structure comprises a surface resin
composition.

11. The process of claim 10 wherein the surface heat stabilizer is
selected from dipentaerythritol, tripentaerythritol, pentaerythritol and
mixtures of these.

12. An overmolded composite structure comprising: the composite structure
of claim 1 and a second component comprising a polyamide resin
composition and optionally a reinforcing agent selected from glass
fibers, carbon fibers, glass beads, and aramid fibers; and overmolded
onto said first component; wherein the second component is adhered to at
least part of the surface of the first component.

13. A process for making an overmolded composite structure, the process
comprising the step of overmolding a second component onto a composite
structure of claim 1 wherein the second component comprises a polyamide
resin composition and optionally a reinforcing agent selected from glass
fibers, carbon fibers, glass beads, and aramid fibers.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional
Application No. 61/408,166, filed Oct. 29, 2010, which is now pending,
the entire disclosure of which is incorporated herein by reference; and
U.S. Provisional Application Nos. 61/410,093, filed Nov. 4, 2010;
61/410,100, filed Nov. 4, 2010; 61/410,104, filed Nov. 4, 2010; and
61/410,108, filed Nov. 4, 2010; all of which are now pending, the entire
disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to the field of composite structures
having improved heat aging, processes for making them, and end use
articles.

BACKGROUND OF THE INVENTION

[0003] With the aim of replacing metal parts for weight saving and cost
reduction while having comparable or superior mechanical performance,
structures based on composite materials comprising a polymer matrix
containing a fibrous material have been developed. With this growing
interest, fiber reinforced plastic composite structures have been
designed because of their excellent physical properties resulting from
the combination of the fibrous material and the polymer matrix and are
used in various end-use applications. Manufacturing techniques have been
developed for improving the impregnation of the fibrous material with a
polymer matrix to optimize the properties of the composite structure.

[0004] In highly demanding applications, such as for example structural
parts in automotive and aerospace applications, composite materials are
desired due to a unique combination of light weight, high strength and
temperature resistance.

[0005] High performance composite structures can be obtained using
thermosetting resins or thermoplastic resins as the polymer matrix.
Thermoplastic-based composite structures present several advantages over
thermoset-based composite structures including the ability to be
post-formed or reprocessed by the application of heat and pressure.
Additionally, less time is needed to make the composite structures
because no curing step is required and they have increased potential for
recycling.

[0006] Among thermoplastic resins, polyamides are particularly well suited
for manufacturing composite structures. Thermoplastic polyamide
compositions are desirable for use in a wide range of applications
including parts used in automobiles, electrical/electronic parts,
household appliances and furniture because of their good mechanical
properties, heat resistance, impact and chemical resistance and because
they may be conveniently and flexibly molded into a variety of articles
of varying degrees of complexity and intricacy.

[0007] With the aim of improving the manufacturing process for making
composite structures and integrated composite structures and allowing an
easier, shorter and uniform mixing or impregnation of fibrous materials,
several ways have been developed to decrease the melt viscosity of the
polymer matrix. By having a low melt viscosity, polymer compositions flow
faster and are thus easier to process. By reducing the melt viscosity of
the polymer matrix, the time needed to reach the desired degree of mixing
may be shortened, thereby increasing the overall manufacturing speed and
thus leading to increased productivity.

[0008] However, the use of a low melt viscosity polyamide composition for
improving or accelerating the mixing or impregnation of fibrous materials
may lead to composite structures that are not ideal for highly demanding
applications such as the automotive field due to inferior mechanical and
heat aging properties.

[0009] The addition of heat stabilizers to polymer matrix compositions can
allow for a higher impregnation temperature which lowers the viscosity of
the polymer matrix composition but these heat stabilizers can also
interfere with adhesion of the overmolding resin.

[0011] US 2010/0120959 discloses polyamide compositions comprising a
transition metal ion-modified clay as a heat-stabilizer. The metal ion
for use in modifying the clay is a transition metal selected from the
transition metals in Group IB, VIIB, VIIB and VIII of the Periodic Table
and combinations thereof.

[0012] US 2009/0269532 teaches a multilayer structure comprising at least
one stabilized layer. The stabilized layer is stabilized with 0.5%
stabilizer based on copper iodide and potassium iodide. This stabilizer
is constituted of 10% copper iodide, 80% potassium iodide and 10% zinc
stearate.

[0013] US 2008/0146718 discloses a non-fibrous-reinforced thermoplastic
molding composition comprising a metal powder as a heat stabilizer
wherein the metal powder has a weight average particle size of at most 1
mm and the metal in the metal powder is selected from the group
consisting of elementary metals from Group VB, VIIB, VIIB and VIIIB of
the Periodic Table, and mixtures thereof.

[0014] U.S. Pat. No. 7,811,671 discloses films which comprise polyamide
compositions which use potassium iodide and cuprous iodide with a
magnesium stearate binder as a heat stabilizer.

[0015] FR 2,158,422 discloses a composite structure made of a low
molecular weight polyamide matrix and reinforcing fibers. Due to the low
molecular weight of the polyamide, the polyamide has low viscosity. The
low viscosity of the polyamide matrix allows an efficient impregnation of
the reinforcing fibers.

[0016] U.S. Pat. No. 7,323,241 discloses a composite structure made of
reinforcing fibers and a branched polyamide resin having a star
structure. The disclosed polyamide having a star structure is said to
exhibit a high fluidity in the molten state thus making possible a good
impregnation of the reinforcing fibers so as to form a composite
structure having good mechanical properties.

[0017] WO 2007/149300 discloses a semi-aromatic polyamide composite
article comprising a component comprising a fiber-reinforced material
comprising a polyamide matrix composition, an overmolded component
comprising a polyamide composition, and an optional tie layer there
between, wherein at least one of the polyamide compositions is a
semi-aromatic polyamide composition

[0018] However, there is still a need for a composite structure comprising
a matrix resin composition that can rapidly and efficiently impregnate a
fibrous material and wherein the composite structure exhibits good
long-term heat stability.

SUMMARY OF THE INVENTION

[0019] There is disclosed and claimed herein a composite structure and an
overmolded composite structure comprising a combination of heat
stabilizers.

[0020] The composite structure comprises:

[0021] a polyamide matrix resin composition comprising [0022] from 0.1
to at or about 3 weight percent of a copper based heat stabilizer based
on the weight of the polyamide matrix resin composition;

[0023] a fibrous material selected from woven or non-woven structures,
felts, knits, braids, textiles, fibrous battings or mats, and
combinations of these; and

[0024] a polyamide surface resin composition comprising

[0025] 0.1 to 3 weight percent of surface heat stabilizer based on the
weight of the polyamide surface resin composition;

wherein: the surface heat stabilizer is different than the copper based
heat stabilizer; and the fibrous material is impregnated with the
polyamide matrix resin composition.

[0026] Preferably, in the composite structures of the invention, the
surface heat stabilizer is selected from dipentaerythritol,
tripentaerythritol, pentaerythritol and mixtures of these. More
preferably, the surface heat stabilizer is selected from
dipentaerythritol.

[0027] In a second aspect, the invention provides articles prepared from
the composite structures of the invention.

[0028] In yet another aspect, the invention discloses and claims a process
to manufacture the composite structure of the invention.

[0029] In yet another aspect, the invention discloses and claims
overmolded composite structures and a process to manufacture the
overmolded composite structure.

DETAILED DESCRIPTION

[0030] The composite structures according to the present invention offer
good thermal stability during their manufacture, good heat aging
properties, retention of mechanical properties after long-term high
temperature exposure.

[0031] For making overmolded composite structures and to increase the
performance of polymers, it is often desired to "overmold" one or more
polymer compositions onto the top portion, or all of the surfaces of a
component so as to surround or encapsulate the component structure.
Overmolding involves molding a second polymer (second component) directly
onto one or more surfaces of the component structure (first component) to
form an overmolded composite structure, wherein the first component and
second component are adhered one to the other at least at one interface
to make an overmolded composite structure. The first component can be a
composite structure and the first component can comprise various
polymeric and fibrous materials. The polymer compositions of this
invention used to impregnate fibrous materials of the first component or
composite structure (i.e. the matrix polymer composition) are different
compositions from the resin(s) which comprise the surface of the first
component or composite structure (i.e. surface resin composition) but
they may comprise the same polyamide polymer. The first component or
composite structure and the second component of the overmolded composite
structure are desired to have good adhesion to each other. The composite
structure and/or overmolded composite structure are desired to have good
dimensional stability and retain their mechanical properties under
adverse conditions, including thermal cycling.

[0032] Polyamides are excellent examples of polymers that can be used to
make composite structures or overmolded composite structures due to their
excellent mechanical properties. Unfortunately, polyamide compositions
may suffer from an unacceptable deterioration of their mechanical
properties during their manufacture and upon long-term high temperature
exposure during use and therefore, they may be non-ideal for making
overmolded composite structures used in highly demanding applications
such as the automotive field. Indeed, there is a current and general
desire in the automotive field to have high temperature resistant,
lightweight structures. Such high temperature resistant structures are
required to maintain their mechanical properties when they are exposed to
temperatures higher than 120° C. or even higher than 200°
C., such as those often reached in underhood areas of automobiles or to
maintain their mechanical properties at an intermediate temperature, such
as for example 90° C., for long periods of time. When plastic
parts are exposed to such combinations of time and temperature, it is a
common phenomenon that the mechanical properties tend to decrease due to
the thermo-oxidation of the polymer. This phenomenon is called heat
aging.

[0033] Unfortunately, the existing technologies fail to combine easy and
efficient processability in terms of the impregnation rate of the fibrous
material by a polymer with good thermal resistance, good retention of
mechanical properties against long-term high temperature exposure, and
excellent adhesion to overmolding compositions.

[0034] The present invention relates to composite structures and processes
to make them. The composite structure according to the present invention
comprises at least one polyamide matrix resin impregnated into at least
one fibrous material and wherein the polyamide matrix resin comprises a
copper based heat stabilizer. The composite structure additionally
comprises a polyamide surface resin composition comprising a surface heat
stabilizer. Preferably, the surface heat stabilizer is selected from
dipentaerythritol, tripentaerythritol, pentaerythritol and mixtures of
these and even more preferably, the surface heat stabilizer is
dipentaerythritol. The polyamide used in the polyamide matrix resin
composition and the polyamide surface resin composition can be the same
polyamide or different polyamides or blends of two or more polyamides.

[0035] The second component used to overmold the first component or
composite structure is a polyamide resin composition optionally
comprising a copper based heat stabilizer and optionally comprising a
reinforcing agent.

Definitions

[0036] As used throughout the specification, the phrases "about" and "at
or about" are intended to mean that the amount or value in question may
be the value designated or some other value about the same. The phrase is
intended to convey that similar values promote equivalent results or
effects according to the invention.

[0037] As used herein, the term "overmolded composite structure" means a
structure comprising a first component or a composite structure and a
second component. The second component is overmolded onto the first
component or composite structure to make the overmolded composite
structure.

[0038] As used herein, the term "first component" or "composite structure"
means a composition comprising at least one polyamide matrix resin
composition, at least one fibrous material, and a polyamide surface resin
composition. The polyamide surface resin composition is the outermost
surface of the entire surface of the first component, or composite
structure, or only a portion of the surface of the first component or
composite structure depending on what percentage of the first component
surface or composite structure surface is to be overmolded. The polyamide
surface resin composition can be the outermost top, the outermost bottom,
or both the outermost top and outermost bottom surfaces of the first
component or composite structure.

[0039] As used herein, the term "polyamide matrix resin" means the
polyamide resin composition that is used to impregnate the fibrous
material.

[0040] As used herein, the term "surface heat stabilizer" means a
stabilizer used in the polyamide surface resin composition. The surface
heat stabilizer is not a copper based heat stabilizer and does not
contain copper or copper ions.

[0041] As used herein, the term "fibrous material" means a material that
is any suitable mat, fabric, or web form known to those skilled in the
art. The fibers or strands used to form the fibrous material are
interconnected (i.e. at least one fiber or strand is touching at least
one other fiber or strand to form a continuous material) or touching each
other so that a continuous mat, web or similar structure is formed.

[0042] As used herein, the term "polyamide surface resin" means a
polyamide composition which comprises the outer surface of the first
component or composite structure. The polyamide surface resin composition
can comprise the entire outer surface of the first component or composite
structure or a portion of the outer surface of the first component or
composite structure depending on the end use.

[0043] As used herein, the term "copper based heat stabilizer" means a
heat stabilizer that comprises a copper halide compound and a alkali
metal halide compound or combinations of different copper halides or
alkali metal halides.

[0044] As used herein, the term "second component" or "overmolding
component" means a composition comprising a polyamide resin composition
and optionally a reinforcing agent. The second component is used to
overmold the first component or composite structure.

[0045] As used herein, the term "overmolded" means molding and casting
processes used to overmold a substrate, structure, or article with a
polymeric composition. It is the process of molding over a substrate,
structure, article, wherein the overmolding polymeric composition is
bonded to and becomes an integral part of the substrate, structure, or
article (i.e. the exterior part) upon cooling.

[0046] As used herein, the term "impregnated" means the polyamide matrix
resin composition flows into the cavities and void spaces of the fibrous
material

[0047] As used herein, the term "bond strength" means the strength of the
bond between the first component or composite structure and second
component or overmolding component of the overmolded composite structure.

[0048] As used herein, the term "heat aging" means exposing the component
structure, the composite structure and/or the overmolded composite
structure to elevated temperatures for a given period of time.

[0049] As used herein, the term "high temperature long-term exposure"
refers to a combination of exposure factors, i.e. time and temperature.
Polymers which demonstrate heat aging performance under lab conditions or
under conditions of the lifetime of the polymers such as those reached in
underhood areas of automobiles (e.g. at a temperature at or in excess of
120° C., preferably at or in excess of 160° C., more
preferably at or in excess of 180° C. and still more preferably at
or in excess of 200° C. and the aging or exposure being at or in
excess of 500 hours and preferably at or in excess of 1000 hours) can be
shown to exhibit similar performance at lower temperatures for a much
longer period of aging or exposure. The temperature dependence of the
rate constants of polymer degradation is known from the literature such
as for example in Journal of Materials Science, 1999, 34, 843-849, and is
described by Arrhenius law; as an example aging at 180° C. for 500
hours is more-or-less equivalent to aging at 80° C. for 12 years.

First Component or Composite Structure

[0050] The first component or composite structure comprises one or more
fibrous materials impregnated with one or more polyamide matrix resin
compositions and comprises one or more surface resin compositions. The
first component or composite structure can have a total thickness of from
about 50 to 20000 microns, preferably from about 50 to 5000 microns, more
preferably from about 500 to 3000 microns, and most preferably from about
800 to 2000 microns. The first component or composite structure can have
multiple fibrous materials.

[0051] The polyamide surface resin composition may be both the top and
bottom surface of the first component or composite structure (essentially
completely encapsulating the first component or composite structure).
Such a composition may be useful when it is desired to encapsulate or
overmold the entire surface of the first component or composite structure
with the second component. The polyamide surface resin composition may
also be only the top or bottom surface, or a portion of the top or bottom
surface of the first component or composite structure depending on what
percentage of the first component surface or composite structure surface
is to be overmolded.

[0052] If the first component or composite structure is to be overmolded
only on one surface or part of surface, then the polyamide surface resin
composition may be present only on the surface or portion of the surface
that is to be overmolded by the second component.

Fibrous Material

[0053] The fibrous material impregnated with the polyamide matrix resin
composition may be in any suitable mat, fabric, or web form known to
those skilled in the art. Suitable examples of such fibrous materials
include woven or nonwoven fabrics or mats, unidirectional strands of
fiber, and the like and different layers of fibrous material in the first
component or composite structure may be formed from different kinds of
fibers, mats, or fabrics. The first component or composite structure may
contain multiple layers of fibrous materials which are impregnated with
one or more polyamide matrix resin compositions. Additionally, any given
fibrous layer may be formed from two or more kinds of fibers (e.g.,
carbon and glass fibers). The fibers may be unidirectional, bi
directional, or multidirectional. Preimpregnated unidirectional fibers
and fiber bundles may be formed into woven or nonwoven mats or other
structures suitable for forming the fibrous material. The fibrous
material may be in the form of a unidirectional preimpregnated material
or a multiaxial laminate of a preimpregnated material.

[0054] The fibrous material is preferably selected from woven or non-woven
structures (e.g., mats, felts, fabrics and webs) textiles, fibrous
battings, a mixture of two or more materials, and combinations thereof.
Non-woven structures can be selected from random fiber orientation or
aligned fibrous structures. Examples of random fiber orientation include
without limitation material which can be in the form of a mat, a needled
mat or a felt. Examples of aligned fibrous structures include without
limitation unidirectional fiber strands, bidirectional strands,
multidirectional strands, multi-axial textiles. Textiles can be selected
from woven forms, knits, braids and combinations thereof.

[0055] As used herein, the term "a fibrous material being impregnated with
a polyamide matrix resin composition" means that the polyamide matrix
resin composition encapsulates and embeds the fibrous material so as to
form an interpenetrating network of fibrous material substantially
surrounded by the matrix resin composition. For purposes herein, the term
"fiber" is defined as a macroscopically homogeneous body having a high
ratio of length to width across its cross-sectional area perpendicular to
its length. The fiber cross section can be any shape, but is typically
round or oval shaped. Depending on the end-use application of the
composite structure and/or overmolded composite structure and the
required mechanical properties, more than one fibrous material can be
used, either by using several of the same fibrous materials or a
combination of different fibrous materials. An example of a combination
of different fibrous materials is a combination comprising a non-woven
structure such as for example a planar random mat which is placed as a
central layer and one or more woven continuous fibrous materials that are
placed as outside layers or layers above or below or both above and below
the central layer. Such a combination allows an improvement of the
processing and thereof of the homogeneity of the first component or
composite structure thus leading to improved mechanical properties of the
composite structure and/or overmolded composite structure. The fibrous
material may be made of any suitable material or a mixture of materials
provided that the material or the mixture of materials withstand the
processing conditions used during the impregnation by the polyamide
matrix resin composition and the polyamide surface resin composition and
during overmolding of the first component or composite structure by the
second component.

[0056] Preferably, the fibrous material comprises glass fibers, carbon
fibers, aramid fibers, graphite fibers, metal fibers, ceramic fibers,
natural fibers or mixtures thereof; more preferably, the fibrous material
comprises glass fibers, carbon fibers, aramid fibers, natural fibers or
mixtures thereof; and still more preferably, the fibrous material
comprises glass fibers, carbon fibers and aramid fibers or mixture
mixtures thereof. By natural fiber, it is meant any material of plant
origin or of animal origin. When used, the natural fibers are preferably
derived from vegetable sources such as for example from seed hair (e.g.
cotton), stem plants (e.g. hemp, flax, bamboo; both bast and core
fibers), leaf plants (e.g. sisal and abaca), agricultural fibers (e.g.,
cereal straw, corn cobs, rice hulls and coconut hair) or lignocellulosic
fiber (e.g. wood, wood fibers, wood flour, paper and wood-related
materials). As mentioned above, more than one fibrous materials can be
used. A combination of fibrous materials made of different fibers can be
used such as for example a first component or composite structure
comprising one or more central layers made of glass fibers or natural
fibers and one or more outer layers (relative to central layer) made of
carbon fibers or glass fibers. Preferably, the fibrous material is
selected from woven structures, non-woven structures or combinations
thereof, wherein said structures are made of glass fibers and wherein the
glass fibers are E-glass filaments with a diameter between 8 and 30 μm
and preferably with a diameter between 10 to 24 μm. The fibrous
material used in the first component or composite structure of the
invention cannot be chopped fibers or particles. To be clear, the fibrous
material in the first component or composite structure cannot be fibers
or particles which are not interconnected to form a continuous mat, web
or similar layered structure. In other words, they cannot be independent
or single fibers or particles surrounded by the polyamide matrix resin
composition.

[0057] The fibrous material may further comprise a thermoplastic material,
for example the fibrous material may be in the form of commingled or
co-woven yarns or a fibrous material impregnated with a powder made of a
thermoplastic material that is suited to subsequent processing into woven
or non-woven forms, or a mixture for use as a uni-directional material.

[0058] Preferably, the ratio between the fibrous material and the polymer
materials in the first component or composite structure (i.e. the fibrous
material in combination with the matrix resin composition and the surface
resin composition), is at least 30 percent fibrous material and more
preferably between 40 and 60 percent fibrous material, the percentage
being a volume-percentage based on the total volume of the first
component structure or composite structure.

Copper Based Heat Stabilizer

[0059] The heat stabilizer used in the polyamide matrix resin composition
(first component or composite structure) and optionally in the second
component is a copper halide based inorganic heat stabilizer. The heat
stabilizer comprises at least one copper halide or copper acetate and at
least one alkali metal halide. Nonlimiting examples of copper halide
include copper iodide and copper bromide. The alkali metal halide is
selected from the group consisting of the iodides and bromides of
lithium, sodium, and potassium with potassium iodide or bromide being
preferred. Preferably, the copper based heat stabilizer is a mixture of
10 to 50 weight percent copper halide, 50 to 90 weight percent potassium
iodide, and from zero to 15 weight percent metal stearate. Even more
preferably, the copper based heat stabilizer is a mixture of 10 to 30
weight percent copper halide, 70 to 90 weight percent potassium iodide,
and from zero to 15 weight percent metal stearate and most preferably the
copper based heat stabilizer is a mixture of 10 to 20 weight percent
copper halide, 75 to 90 weight percent potassium iodide, and from zero to
12 weight percent metal stearate. An example of a copper based heat
stabilizer of the invention is Polyadd P201 from Ciba Specialty Chemicals
comprising a blend of 7:1:1 weight ratio (approximately 78:11:11 percent
ratio by weight) of potassium iodide, cuprous iodide, and aluminum
stearate respectively. A preferred heat stabilizer is a mixture of copper
iodide and potassium iodide (CuI/KI). The heat stabilizer is present in
an amount from at or about 0.1 to at or about 3 weight percent,
preferably from at or about 0.1 to at or about 1.5 weight percent, or
more preferably from at or about 0.1 to at or about 1.0 weight percent,
the weight percentage being based on the total weight of the polyamide
matrix resin composition in the first component or composite structure or
based on the total weight of the polyamide resin composition of the
second component, as the case may be. The amount of copper halide based
heat stabilizer in the polyamide matrix resin composition or the
polyamide resin composition of the second component will depend on the
anticipated use. If extremely high temperature environments are
envisioned, then a higher concentration of copper halide heat stabilizer
is needed.

Surface Heat Stabilizer

[0060] The surface heat stabilizer of the polyamide surface resin
composition is different than the copper based heat stabilizer of the
polyamide matrix resin composition. The one or more surface heat
stabilizers in the polyamide surface resin composition are present in an
amount from 0 to at or about 3 weight percent, preferably from at or
about 0.1 to at or about 3 weight percent, more preferably from at or
about 0.1 to at or about 1 weight percent, or more preferably from at or
about 0.1 to at or about 0.7 weight percent, the weight percentage being
based on the total weight of the polyamide surface resin composition in
the first component or composite structure.

[0061] The surface heat stabilizer used in the polyamide surface resin
composition can be any heat stabilizer as long as it is not a copper
halide based heat stabilizer. Heat stabilizers useful in the polyamide
surface resin composition include polyhydric alcohols having more than
two hydroxyl groups. The one or more polyhydric alcohols may be
independently selected from aliphatic hydroxylic compounds containing
more than two hydroxyl groups, aliphatic-cycloaliphatic compounds
containing more than two hydroxyl groups, cycloaliphatic compounds
containing more than two hydroxyl groups and saccharides containing more
than two hydroxyl groups.

[0062] An aliphatic chain in the polyhydric alcohol can include not only
carbon atoms but also one or more hetero atoms which may be selected, for
example, from nitrogen, oxygen and sulphur atoms. A cycloaliphatic ring
present in the polyhydric alcohol can be monocyclic or part of a bicyclic
or polycyclic ring system and may be carbocyclic or heterocyclic. A
heterocyclic ring present in the polyhydric alcohol can be monocyclic or
part of a bicyclic or polycyclic ring system and may include one or more
hetero atoms which may be selected, for example, from nitrogen, oxygen
and sulphur atoms. The one or more polyhydric alcohols may contain one or
more substituents, such as ether, carboxylic acid, carboxylic acid amide
or carboxylic acid ester groups.

[0064] Preferred polyhydric alcohols include those having a pair of
hydroxyl groups which are attached to respective carbon atoms which are
separated one from another by at least one atom. Especially preferred
polyhydric alcohols are those in which a pair of hydroxyl groups is
attached to respective carbon atoms which are separated one from another
by a single carbon atom. Preferably, the one or more polyhydric alcohols
comprised in the polyamide surface resin composition described herein are
independently selected from pentaerythritol, dipentaerythritol,
tripentaerythritol, di-trimethylopropane, D-mannitol, D-sorbitol, xylitol
and mixtures thereof. More preferably, the one or more polyhydric
alcohols comprised in the polyamide composition described herein are
independently selected from dipentaerythritol, tripentaerythritol,
pentaerythritol and mixtures thereof. Still more preferably, the one or
more polyhydric alcohols comprised in the polyamide surface resin
composition described herein are dipentaerythritol and/or
pentaerythritol.

[0065] The one or more polyhydric alcohols are present in the polyamide
surface resin composition described herein from 0.25 weight percent to 15
weight percent, more preferably from 0.5 weight percent to 10 weight
percent and still more preferably from 0.5 weight percent to 5 weight
percent, the weight percentages being based on the total weight of the
polyamide surface resin composition in the first component or composite
structure.

[0066] Preferably, the one or more polyhydric alcohols comprised in the
polyamide composition described herein are dipentaerythritol and/or
pentaerythritol and are present in the polyamide surface resin
composition described herein from at or about 0.1 to at or about 3 weight
percent, more preferably from at or about 0.1 to at or about 1 weight
percent, or more preferably from at or about 0.1 to at or about 0.7
weight percent, the weight percentage being based on the total weight of
the polyamide surface resin composition in the first component or
composite structure.

Polyamide Resins

[0067] Polyamide resins used in the manufacture of the composite structure
of the invention and/or in the manufacture of the overmolded composite
structure are condensation products of one or more dicarboxylic acids and
one or more diamines, and/or one or more aminocarboxylic acids, and/or
ring-opening polymerization products of one or more cyclic lactams. The
polyamide resins are selected from fully aliphatic polyamide resins,
semi-aromatic polyamide resins and mixtures thereof. The term
"semi-aromatic" describes polyamide resins that comprise at least some
aromatic carboxylic acid monomer(s) and aliphatic diamine monomer(s), in
comparison with "fully aliphatic" which describes polyamide resins
comprising aliphatic carboxylic acid monomer(s) and aliphatic diamine
monomer(s).

[0068] Fully aliphatic polyamide resins are formed from aliphatic and
alicyclic monomers such as diamines, dicarboxylic acids, lactams,
aminocarboxylic acids, and their reactive equivalents. A suitable
aminocarboxylic acid includes 11-aminododecanoic acid. In the context of
this invention, the term "fully aliphatic polyamide resin" refers to
copolymers derived from two or more such monomers and blends of two or
more fully aliphatic polyamide resins. Linear, branched, and cyclic
monomers may be used.

[0070] Semi-aromatic polyamide resins are homopolymers, copolymers,
terpolymers, or higher polymers wherein at least a portion of the acid
monomers are selected from one or more aromatic carboxylic acids. The one
or more aromatic carboxylic acids can be terephthalic acid or mixtures of
terephthalic acid and one or more other carboxylic acids, like
isophthalic acid, substituted phthalic acid such as for example
2-methylterephthalic acid and unsubstituted or substituted isomers of
naphthalenedicarboxylic acid, wherein the carboxylic acid component
preferably contains at least 55 mole percent of terephthalic acid (the
mole percent being based on the carboxylic acid mixture). Preferably, the
one or more aromatic carboxylic acids are selected from terephthalic
acid, isophthalic acid and mixtures thereof and more preferably, the one
or more carboxylic acids are mixtures of terephthalic acid and
isophthalic acid, wherein the mixture preferably contains at least 55
mole percent of terephthalic acid. Furthermore, the one or more
carboxylic acids can be mixed with one or more aliphatic carboxylic
acids, like adipic acid; pimelic acid; suberic acid; azelaic acid;
sebacic acid and dodecanedioic acid, adipic acid being preferred. More
preferably the mixture of terephthalic acid and adipic acid comprised in
the one or more carboxylic acids mixtures of the semi-aromatic polyamide
resin contains at least 25 mole percent of terephthalic acid.
Semi-aromatic polyamide resins comprise one or more diamines that can be
chosen among diamines having four or more carbon atoms, including, but
not limited to tetramethylene diamine, hexamethylene diamine,
octamethylene diamine, nonamethylene diamine, decamethylene diamine,
2-methylpentamethylene diamine, 2-ethyltetramethylene diamine,
2-methyloctamethylene diamine; trimethylhexamethylene diamine,
bis(p-aminocyclohexyl)methane; m-xylylene diamine; p-xylylene diamine
and/or mixtures thereof. Suitable examples of semi-aromatic polyamide
resins include poly(hexamethylene terephthalamide) (polyamide 6,T),
poly(nonamethylene terephthalamide) (polyamide 9,T), poly(decamethylene
terephthalamide) (polyamide 10,T), poly(dodecamethylene terephthalamide)
(polyamide 12,T), hexamethylene adipamide/hexamethylene terephthalamide
copolyamide (polyamide 6,T/6,6), hexamethylene
terephthalamide/hexamethylene isophthalamide (6,T/6,I), poly(m-xylylene
adipamide) (polyamide MXD,6), hexamethylene adipamide/hexamethylene
terephthalamide copolyamide (polyamide 6,T/6,6), hexamethylene
terephthalamide/2-methylpentamethylene terephthalamide copolyamide
(polyamide 6,T/D,T), hexamethylene adipamide/hexamethylene
terephthalamide/hexamethylene isophthalamide copolyamide (polyamide
6,6/6,T/6,I); poly(caprolactam-hexamethylene terephthalamide) (polyamide
6/6,T) and copolymers and blends of the same. Preferred examples of
semi-aromatic polyamide resins comprised in the polyamide composition
described herein include PA6,T; PA6,T/6,6, PA6,T/6,I; PAMXD,6; PA6,T/D,T
and copolymers and blends of the same.

[0071] Any combination of aliphatic or semi-aromatic polyamides can be
used as the polyamide for the polyamide matrix resin composition,
polyamide surface resin composition, and the polyamide resin of the
second component. It is within the normal skill of one in the art to
select appropriate combinations of polyamides depending on the end use.

Second Component or Overmolding Component

[0072] The second component of the overmolded composite structure used to
overmold the first component or composite structure is a polyamide resin
composition optionally comprising a copper based heat stabilizer as
described above and optionally a reinforcing agent. The one or more
polyamides may be the same or different from the one or more polyamides
of the first component or composite structure matrix resin and surface
resin composition.

Reinforcing Agent

[0073] The polyamide resin composition of the second component may further
comprise one or more reinforcing agents such as glass fibers, glass
flakes, carbon fibers, mica, wollastonite, calcium carbonate, talc,
calcined clay, kaolin, magnesium sulfate, magnesium silicate, barium
sulfate, titanium dioxide, sodium aluminum carbonate, barium ferrite, and
potassium titanate. The reinforcing agent in the second component cannot
be a mat or woven fabric such as those used in the first component or
composite structure. Preferably, the reinforcing agent comprises
independent fibers or particles uniformly blended into the polyamide. Any
reinforcing agent used in the second component must allow the polyamide
resin composition to be injection or flow molded. When present, the one
or more reinforcing agents are present in an amount from at or about 1 to
at or about 60 weight percent, preferably from at or about 1 to at or
about 40 weight percent, or more preferably from at or about 1 to at or
about 35 weight percent, the weight percentages being based on the total
weight of the polyamide resin composition of the second component.

Overmolded Composite Structure

[0074] Addition of surface and copper based heat stabilizers to the
components of the invention improves thermal stability of the first
component or composite structure and optionally of the second component
during processing as well as upon use and time of the composite structure
or overmolded composite structure. In addition to the improved heat
stability, the presence of heat stabilizers may allow an increase of the
temperature that is used during the impregnation of the fibrous material,
thus reducing the melt viscosity of the matrix resin described herein. As
a consequence of a reduced melt viscosity of the matrix resin,
impregnation rates of the fibrous material may be increased.

[0075] The use of different heat stabilizers in the polyamide matrix resin
composition and the polyamide surface resin composition of the first
component or composite structure is an important aspect of the invention.
The use of a copper based heat stabilizer in the polyamide matrix resin
composition in combination with a surface heat stabilizer in the
polyamide surface resin composition improves heat aging properties of the
composite structure.

[0076] In a preferred embodiment, the surface heat stabilizer is selected
from dipentaerythritol, tripentaerythritol, pentaerythritol and mixtures
of these and the matrix heat stabilizer in the matrix resin composition
is a copper based heat stabilizer.

[0077] The overmolded composite structure comprises a second component
overmolded onto the first component or composite structure. The second
component is adhered to the first component or composite structure
described above over at least a portion of the top or bottom surface of
the first component or composite structure, the entire top or bottom
surface of the first component or composite structure, or both, or
completely encapsulates the first component or composite structure.
Regardless of what portion of the surface of the first component or
composite structure is overmolded, the surface of the first component or
composite structure that is overmolded must comprise the polyamide
surface resin composition to assure good bond strength of the first and
second components. The second component comprises one or more polyamide
resin compositions selected from aliphatic polyamide resins,
semi-aromatic polyamide resins, or combinations thereof such as those
described above.

Additives

[0078] The polyamide resin of any component of the composite structure or
overmolded composite structure may further comprise one or more common
additives, including, without limitation, ultraviolet light stabilizers,
flame retardant agents, flow enhancing additives, lubricants, antistatic
agents, coloring agents (including dyes, pigments, carbon black, and the
like), nucleating agents, crystallization promoting agents and other
processing aids or mixtures thereof known in the polymer compounding art.

[0079] Fillers, modifiers and other ingredients described above may be
present in amounts and in forms well known in the art, including in the
form of so-called nano-materials where at least one of the dimensions of
the particles is in the range of 1 to 1000 nm.

[0080] Preferably, any additives, including heat stabilizers but excluding
fibrous materials used in the first component or composite structure of
the invention, added to the polyamide resins used in any component of the
composite structure and/or overmolded composite structure are
well-dispersed within the polyamide resin. Any melt-mixing method may be
used to combine the polyamide resins and additives of the present
invention. For example, the polyamide resins and additives may be added
to a melt mixer, such as, for example, a single or twin-screw extruder; a
blender; a single or twin-screw kneader; or a Banbury mixer, either all
at once through a single step addition, or in a stepwise fashion, and
then melt-mixed. When adding the polyamide resins and additional
additives in a stepwise fashion, part of the polyamide resin and/or
additives are first added and melt-mixed with the remaining polyamide
resin(s) and additives being subsequently added and further melt-mixed
until a well-mixed or homogeneous composition is obtained.

[0081] The overmolded composite structure according to the present
invention may be manufactured by a process comprising a step of
overmolding the first component or composite structure with the second
component. By "overmolding", it is meant that the second component is
molded or extruded onto at least one portion of the surface of the first
component or composite structure.

[0082] In one example of an overmolding process, the second component is
injected into a mold already containing the first component or composite
structure, the latter having been manufactured beforehand as described
hereafter, so that the first and second components are adhered to each
other over at least a portion of the surface of the first component or
composite structure. The first component or composite structure is
positioned in a mold having a cavity defining the outer surface of the
final overmolded composite structure. The second component may be
overmolded on one side or on both sides of the first component or
composite structure and it may fully or partially encapsulate the first
component or composite structure. After having positioned the first
component or composite structure in the mold, the second component is
then introduced in molten form. The two components are preferably adhered
together by injection or compression molding as an overmolding step, and
more preferably by injection molding.

[0083] The first component or composite structure can be made by a process
that comprises a step of impregnating the fibrous material with the
polyamide matrix resin composition, wherein at least a portion of the
surface of the first component or composite structure comprises the
polyamide surface resin composition. Preferably, the fibrous material is
impregnated with the polyamide matrix resin composition by
thermopressing. During thermopressing, the fibrous material(s), the
polyamide matrix resin composition and the polyamide surface resin
composition undergo heat and pressure in order to allow the polymers to
melt and penetrate through the fibrous material and, therefore, to
impregnate said fibrous material.

[0084] Typically, thermopressing is made at a pressure between 2 and 100
bars and more preferably between 10 and 40 bars and a temperature which
is above the melting point of the polyamide matrix resin composition and
the polyamide surface resin composition, preferably at least about
20° C. above the melting point to enable a proper impregnation.
Heating may be done by a variety of means, including contact heating,
radiant gas heating, infra red heating, convection or forced convection,
induction heating, microwave heating or combinations thereof. Even though
the polyamide compositions are in the melt state during thermopressing,
the polyamide surface resin composition does not migrate from the surface
to any significant degree. After thermopressing, the first component or
composite structure is no longer considered a laminate structure having
separate layers but a unified component structure.

[0085] Due to the improved heat stability obtained by adding a copper
based heat stabilizer to the polyamide matrix resin composition in
combination with a surface heat stabilizer in the polyamide surface resin
composition, the temperature that is used during the impregnation of the
fibrous material can be increased. The reduced melt viscosity of the
polyamide matrix resin composition obtained by this increase of
temperature allows a more rapid impregnation rate of the fibrous material
which translates into a faster overall manufacturing cycle for the
composite structure and/or overmolded composite structure. Addition of
the copper halide based heat stabilizer to the polyamide matrix resin
composition provides heat stability to the polyamide matrix resin
composition during the impregnation.

[0086] Pressure used during the impregnation process can be applied by a
static process or by a continuous process (also known as a dynamic
process), a continuous process being preferred for reasons of speed.
Examples of impregnation processes include without limitation vacuum
molding, in-mold coating, cross-die extrusion, pultrusion, wire coating
type processes, lamination, stamping, diaphragm forming or press-molding,
lamination being preferred.

[0087] One example of a process used to impregnate the fibrous material is
a lamination process. The first step of the lamination process involves
heat and pressure being applied to the fibrous material, the polyamide
matrix resin composition and the polyamide surface resin composition
through opposing pressured rollers or belts in a heating zone, preferably
followed by the continued application of pressure in a cooling zone to
finalize consolidation and cool the impregnated fibrous material by
pressurized means. Examples of lamination techniques include without
limitation calendering, flatbed lamination and double-belt press
lamination. When lamination is used as the impregnating process,
preferably a double-belt press is used for lamination. The lamination
process may comprise various layer combinations of the polyamide matrix
resin composition and the fibrous material. The polyamide surface resin
composition is always used as the top layer or both the top and bottom
layer during the lamination process. For example, the multi-layer
laminate may comprise two polyamide matrix resin composition layers, one
layer of woven continuous glass fiber textile as the fibrous layer, two
polyamide matrix resin composition layers, one layer of woven continuous
glass fiber textile, two polyamide matrix resin composition layers, one
layer of woven continuous glass fiber textile and two polyamide surface
layers to make an 11 layer laminate. After impregnation of the fibrous
materials using the lamination process, the end product is the first
component or composite structure of the invention which can then be
overmolded. A first component or composite structure prepared by this
process is no longer a multi-layer laminate but a unified structure (a
polymer continuum) with no discernable individual layers.

[0088] The polyamide matrix resin composition and the polyamide surface
resin composition can also be applied to the fibrous material by
conventional means such as for example powder coating, film lamination,
extrusion coating or a combination of two or more thereof, provided that
the polyamide surface resin composition is applied on at least a portion
of the surface of the first component or composite structure so as to be
accessible when the polyamide overmolding resin composition is applied
onto at least a portion of the surface of the first component or
composite structure.

[0089] During a powder coating process, a polymer powder which has been
obtained by conventional grinding methods is applied to the fibrous
material. The powder may be applied onto the fibrous material by
scattering, sprinkling, spraying, thermal or flame spraying, or fluidized
bed coating methods. Multiple powder coating layers can be applied to the
fibrous material. Optionally, the powder coating process may further
comprise a step which consists in a post sintering step of the powder on
the fibrous material. The polyamide matrix resin composition and the
polyamide surface resin composition are applied to the fibrous material
such that at least a portion of the surface of the first component or
composite structure comprises the polyamide surface resin composition.
Subsequently, thermopressing is performed on the powder coated fibrous
material, with an optional preheating of the powder coated fibrous
material outside of the pressurized zone.

[0090] During film lamination, one or more films comprising the polyamide
matrix resin composition and one or more films made of the polyamide
surface resin composition which have been obtained by conventional
extrusion methods known in the art such as for example blow film
extrusion, cast film extrusion and cast sheet extrusion are applied to
one or more layers of the fibrous material, e.g. by layering. The
polyamide surface resin composition is again the top or bottom or both
top and bottom layers of the film laminate before thermopressing.
Subsequently, thermopressing is performed on the film laminate comprising
the one or more films made of the polyamide matrix resin composition, the
polyamide surface resin composition, and the one or more fibrous
materials. During thermopressing, the films melt and penetrate around the
fibrous material as a polymer continuum surrounding the fibrous material
with the polyamide matrix resin. The polyamide surface resin composition
remains on the surface of the first component or composite structure.

[0091] During extrusion coating, pellets and/or granulates made of the
matrix resin composition and pellets and/or granulates made of the
surface resin composition are melted and extruded through one or more
flat dies so as to form one or more melt curtains which are then applied
onto the fibrous material by laying down the one or more melt curtains in
a manner similar to the film lamination procedure. Subsequently,
thermopressing is performed on the layered structure to provide the first
component or composite structure of the invention.

[0092] With the aim of improving bond strength between the first component
or composite structure and the second component, the first component or
composite structure is typically heated at a temperature close to but
below the melt temperature of the polyamide matrix resin composition
prior to the overmolding step and then the heated first component or
composite structure is rapidly transferred into the heated mold that will
be used for the overmolding step. Such a preheating step may be done by a
variety of means, including contact heating, radiant gas heating, infra
red heating, convection or forced convection air heating, induction
heating, microwave heating or combinations thereof.

[0093] Depending on the end-use application, the first component or
composite structure may be shaped into a desired geometry or
configuration, or used in sheet form prior to the overmolding step. The
first component or composite structure may be flexible, in which case it
can be rolled and then unrolled for overmolding.

[0094] One process for shaping the first component or composite structure
comprises a step of shaping the first component or composite structure
after the impregnating step. Shaping the first component or composite
structure may be done by compression molding, stamping or any technique
using heat and/or pressure, compression molding and stamping being
preferred. Preferably, pressure is applied by using a hydraulic molding
press. During compression molding or stamping, the composite structure is
preheated to a temperature above the melt temperature of the polyamide
surface resin composition and preferably above the melt temperature of
the polyamide matrix resin composition by heated means and is transferred
to a forming or shaping means such as a molding press containing a mold
having a cavity of the shape of the final desired geometry whereby it is
shaped into a desired configuration and is thereafter removed from the
press or the mold after cooling to a temperature below the melt
temperature of the polyamide surface resin composition and preferably
below the melt temperature of the polyamide matrix resin composition.

[0095] One problem during the manufacture of composite structures and/or
overmolded composite structures is related to the thermo-oxidation and
degradation of the first component or composite structure and especially
the thermal degradation of the surface of the first component or
composite structure during the preheating step(s) described above and
during the shaping step. The present invention not only provides a first
component or composite structure having good heat stability but also
provides a first component or composite structure having excellent bond
strength to the second component. This leads to composite structures
and/or overmolded composite structures that resist degradation of
mechanical performance during exposure to high temperature operational
manufacturing environments and provides excellent long term flexural
strength (bond strength).

[0096] With the aim of improving adhesion between the first component or
composite structure and second component of the overmolded composite
structure, the surface of the first component or composite structure may
be a textured surface so as to increase the relative surface available
for overmolding. Such textured surfaces may be obtained during the
shaping step by using a press or a mold having for example porosities or
indentations on its surface.

[0097] Alternatively, a one step process comprising the steps of shaping
and overmolding the first component or composite structure in a single
molding station may be used. This one step process avoids the step of
compression molding or stamping the first component or composite
structure in a mold or press and avoids the optional preheating step and
the transfer of the preheated first component or composite structure to
the molding station or cavity. During this one step process, the first
component or composite structure is heated outside, adjacent to or within
the molding station at a temperature at which the first component or
composite structure is conformable or shapable during the overmolding
step, preferably the first component or composite structure is heated to
a temperature above its melt temperature. The shape of the first
component or composite structure is conferred by the mold followed by
overmolding.

[0098] The composite structures and/or overmolded composite structures
according to the present invention may be used in a wide variety of
applications such as for example components for automobiles, trucks,
commercial airplanes, aerospace, rail, household appliances, computer
hardware, portable hand held electronic devices, recreation and sports
equipment, structural component for machines, buildings, photovoltaic
equipment or mechanical devices.

[0100] Examples of household appliances include without limitation
washers, dryers, refrigerators, air conditioning and heating. Examples of
recreation and sports include without limitation inline-skate components,
baseball bats, hockey sticks, ski and snowboard bindings, rucksack backs
and frames, and bicycle frames. Examples of structural components for
machines include electrical/electronic parts such as for example housings
for hand held electronic devices, and computers.

[0101] Preferably, the composite structures and/or overmolded composite
structures of the invention are used as under the hood automotive
components where high temperature environments exist.

EXAMPLES

[0102] The following materials were used for preparing examples
(abbreviated as "E" in the table) of composites structures according to
the present invention and comparative examples (abbreviated as "C" in the
table) of composite structures. [0103] Polyamide 1 (PA1): polyamide
comprising adipic acid and 1,6-hexamethylenediamine with a weight average
molecular weight of around 32000 Daltons and is commercially available
from E. I. du Pont de Nemours and Company as PA66. PA1 has a melting
point of about 260° C. to about 265° C. and a glass
transition of about 40° C. to about 70° C., measured by DSC
Instrument first heating scan at 10° C./min. [0104] Polyhydric
alcohol based heat stabilizer (DPE): dipentaerythritol commercially
available from Perstorp Speciality Chemicals AB, Perstorp, Sweden as
Di-Penta 93. [0105] Copper based heat stabilizer (CuI/KI): a blend of
7-1-1 (by weight) blend of potassium iodide, cuprous iodide, and aluminum
stearate, available from Ciba Specialty Chemicals.

Preparation of Films

[0106] Matrix resin compositions and surface resin compositions of example
El and comparative examples C1, C2 and C3 shown in Table 1 were melted or
melt-blended in a twin-screw extruder at about 280° C. The melted
or melt-blended polyamide compositions (Table 1) were made into films by
exiting the extruder through an adaptor and a film die at about
280° C. and cast onto a casting drum oil-heated at 100° C.,
then drawn in air and wound around a core at room temperature. The matrix
and surface resin compositions were made into about 250 micron thick
films. The thickness of the films was controlled by the rate of drawing.

Preparation of the Composite Structures

[0107] Preparation of the Composite Structures_E1,C1, C2 and C3 in Table 1
was accomplished by laminating multiple layers of film of compositions
shown in Table 1, and woven continuous glass fiber textile (prepared from
E-glass fibers having a diameter of 17 microns, sized with 0.4% of a
silane-based sizing agent and a nominal roving tex of 1200 g/km that have
been woven into a 2/2 twill (balanced weave) with an areal weight of 600
g/m2) in the following sequence: two layers of film of surface resin
composition, one layer of woven continuous glass fiber textile, two
layers of film of matrix resin composition, one layer of woven continuous
glass fiber textile, two layers of film of matrix resin composition, one
layer of woven continuous glass fiber textile, and two layers of film of
surface resin composition.

[0108] The Composite Structures were compression molded by a Dake Press
(Grand Haven, Mich.) Model 44-225, Pressure range 0-25KT, with an 8 inch
platten. A 6×6'' specimen of film and glass textile layers as
described above was placed in the mold and heated to a temperature of
about 320° C., held at the temperature for 2 minutes without
pressure, then pressed at the 320° C. temperature with the
following pressures: about 6 bar for about 2 minutes, then with about 22
bar for about 2 additional minutes, and then with about 45 bar for about
2 additional minutes; it was subsequently cooled to ambient temperature.
The thusly formed composite structure had a thickness of about 1.6 mm.
The composite structures had melting ranges between about 245° C.
(onset of melting) to about 268° C. (completion of melting) with
melting peaks at about 260° C. to about 265° C., measured
by DSC Instrument first heating scan at 10° C./min.

Heat Ageing

[0109] The laminates were cut into 1/2'' (about 12.7 mm) by 3'' (about 76
mm) long test specimens (bars) using a MK-377 Tile Saw with a diamond
edged blade and water as a lubricant. Half of the specimens were then
heat aged in a re-circulating air oven at 210° C. for 500 hrs.

Flex Strength of Composite Structures of Table 1

[0110] Flexural Strength was tested on the heat aged test specimens via a
3-point bend test. The apparatus and geometry were according to ISO
method 178, bending the specimen with a 2.0'' support width with the
loading edge at the center of the span. The tests were conducted with 1
KN load at 2 mm/min until fracture. The results are shown in Table 1,
along with test results from the specimens that were not heat aged. The %
retention of flex strength after heat aging is also recorded in Table 1.
It is seen in Table 1 that example E1 containing the copper based heat
stabilizer in the matrix resin composition and DPE in the surface resin
composition retains flexural strength after being heat aged in air at
210° C. for 500 hours (39% flexural strength retention). In
contrast, comparative examples C1, C2 and C3 containing respectively, DPE
in both the matrix and surface resin composition (C1), both copper based
heat stabilizer and DPE in both the matrix and the surface resin
composition (C2) and no heat stabilizers (C3) lose more bond strength
after heat aging in air at 210° C. for 500 hours.

Patent applications in class COATED OR IMPREGNATED WOVEN, KNIT, OR NONWOVEN FABRIC WHICH IS NOT (A) ASSOCIATED WITH ANOTHER PREFORMED LAYER OR FIBER LAYER OR, (B) WITH RESPECT TO WOVEN AND KNIT, CHARACTERIZED, RESPECTIVELY, BY A PARTICULAR OR DIFFERENTIAL WEAVE OR KNIT, WHEREIN THE COATING OR IMPREGNATION IS NEITHER A FOAMED MATERIAL NOR A FREE METAL OR ALLOY LAYER

Patent applications in all subclasses COATED OR IMPREGNATED WOVEN, KNIT, OR NONWOVEN FABRIC WHICH IS NOT (A) ASSOCIATED WITH ANOTHER PREFORMED LAYER OR FIBER LAYER OR, (B) WITH RESPECT TO WOVEN AND KNIT, CHARACTERIZED, RESPECTIVELY, BY A PARTICULAR OR DIFFERENTIAL WEAVE OR KNIT, WHEREIN THE COATING OR IMPREGNATION IS NEITHER A FOAMED MATERIAL NOR A FREE METAL OR ALLOY LAYER